FIELD OF INVENTION
The invention relates to an apparatus for the conveying of green agglomerates, such as pellets, while sieving unwanted materials from the burden.
Ores or intermediate metallurgical products are often pelletized in a moist state. The resulting green pellets, which are generally about 5 to 25 mm in diameter, have a low mechanical strength and for this reason are generally thermally hardened, in most cases on a firing machine. Because green pellets are highly susceptible to mechanical stress, they must be most carefully handled in transit to the firing machine. For this purpose they are conveyed by a seiving roller conveyor, which comprises a series of rollers driven in the direction of conveyance. The clearance between adjacent rollers is smaller than the smallest diameter of the pellets but larger than the particle size of undesired fines, such as broken pellets or abraded fines. The fines fall through these sieving clearances between the rollers so that only pellets having the desired size reach the firing machine (for example German specification DE-PS No. 10 63 811). As the pellets are conveyed on the sieving roller conveyor, the surface of the pellets is roll-formed and the pellets are caused to form a bed of uniform height. Green pellets are sometimes made from ores or concentrates which tend to cake. In that case the rollers of the sieving roller conveyor may become coated with a layer of ore so that the sieving clearances between adjacent rollers become too small for a sifting of the fines and the handling of the pellets may not be as careful as is desired.
It is an object of this invention to provide a sieving roller conveyor which offers a constant sieving clearance for the elimination of fines, broken pellets and the like.
It is another object of this invention to provide a sieving roller conveyor which frees its rollers of buildup of binders and agglomerates which impede the transport and sieving of pellets.
It is yet an object of this invention to reduce maintenance time and costs by reducing the need for manual cleaning of a roller conveyor.
It is still an object of the invention to provide a roller conveyor which can be used in multiple combinations to sort several different sizes of pellets.